Strengthened Diff extension housings

[les M]

When I fitted a BMW diff to my car I made up the mounting using the original stag trailing arms and mountings. I cut up a diff extension housing to use as part of the diff mounting and I was shocked to see just how thin the original extension was in this area. The fault lies I think with the internal machining and not the original casting, no wonder so many have failed.

If you have the diff out of the car then get it reinforced.

Les

[KOY 23]

Good question, i would like to know the answer myself.

I have my diff out on the bench and am not intending to modify it as it all looks good. The backplate has a reinforcing web welded in already, I am reassembling back suspension and will keep a check on the diff extension over the year.

RG

Sorry to disagree but IMHO its a no brainer to modify especially while its out. I would think its very difficult to check, as hairline crack would be difficult to see until it dramatically fails. Going under every time you go out with a good light and magnifying glass is certainly not my idea of fun.

Do it and cross it off the worry list.

John.

[Richard G]

Sorry to disagree but IMHO its a no brainer to modify especially while its out. I would think its very difficult to check, as hairline crack would be difficult to see until it dramatically fails. Going under every time you go out with a good light and magnifying glass is certainly not my idea of fun.

Do it and cross it off the worry list.

John.

Your pic has convinced me to do it, am checking with Chris Witor for replacement!

RG

[Nambo]

Nambo, Richard,
the attached is a picture when mine failed - don't recall any camber or out of line system geometry problems before or after, but it all points to the flange weld (where it split at nose end (as photo)) being of varying qualities from manufacture. It can be seen it is a very small flange / welded ring area to carry such a lot of suspension / diff stress under varying traffic conditions. As my post above, it is a massive "brown trouser moment" when they do go at speed + the absolute fuss and bother with trying to get the car on breakdown truck (nearly broke his winch as with the handbarke held on and the suspension collapsed its like pulling a tank) - so I would always recommend replacement with a reinforced Diff nose extension.

Regards
Ian

Ah! I see, for some reason I was thinking they broke in front of the brackets by the propshaft rather than behind next to the diff, Will get my spare one done.

I still feel a drooping diff caused by elongated subframe mounting holes must put additional strain on that point through.

[wilf]

Maybe, but the torque reaction at the diff nose when you boot it in first will massively outweigh the additional static load you get from what you describe.